Phase transition in organic–inorganic perovskite (C9H19NH3)2 PbI2Br2 of long-chain alkylammonium

Single perovskite slab alkylammonium lead iodides bromides (C9H19NH3)2PbI2Br2 is a new member of the family of hybrid organic-inorganic perovskite compounds. It exhibits a single structural phase transition with changes in the conformation of alkylammonium chains below room temperature. Differential scanning calorimetry (DSC), powder X-ray diffraction and FT-Raman spectroscopy were used to investigate this phase transition. These changes were characterized by a decreased conformational disorder of the methylene units of the alkyl chains. Phase transition was examined in light of the interesting optical properties of this material, as well as the relevance of this system as models for phase transitions in lipid bilayers.

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► DSC, IR, PXRD and FT-Raman are used to investigate (C9H19NH3)2PbI2Br2 compound.
► Geometry optimization by PM3 method implemented in G98 code was performed.
► First-order phase transition induced changes in alkylammonium chains below RT.
► Reliable assignment in IR and Raman bands is presented.
► Reasonable agreement between observed and calculated wavenumbers is reported.